This invention relates to a continuous food processing system whereby an edible plastic food strand of meat or the like is co-extruded with a coated material to be processed into a casing. This coating material may consist of a mixture or gel with a coagulatable protein, and reinforcing means. More specifically this invention relates to a method for the manufacturing whereby the method includes the steps of co-extruding a principally equal layer of gel around an extruded edible product and the treatment of the extruded gel coating with chemical and physical means for coagulation.
Such a method is generally known. These known methods are mainly being used for the co-extrusion of sausage or sausage-like materials. In principal this method involves the extrusion of a cylindrical nucleus of a sausage mix and simultaneously the extrusion around the sausage mix of an outside coating which consists of a gel with a collagen protein. The proteins in the gel are coagulated with the aid of a coagulation means.
The term "coagulation" is a term of art in the production of collagen coated sausage material and is not strictly scientific in the sense in which it is used. Coagulation as it is used in this specification refers to the step involving hardening and stabilization of the casing. This is principally achieved in two ways; firstly by removal of water from the collagen gel, and secondly by cross-linking the collagen fibers.
In the generally known methods the water content gel coating is lowered with the assistance of osmosis by leading the strand of foodstuffs through a concentrated salt bath. Thereafter an air drying step is used to further enhance the strength of the sausage casing. After this treatment the mechanical properties of the casing are insufficient to allow for conventional twist linking, clipping, typing, or hanging of the foodstuff, i.e. sausage, strand. With this usual method it is habitual to crimp the co-extruded strand of foodstuff and cut it into independent elements and these elements are placed in a hot air dryer for the treatment of individual elements (for example drying, smoking etc.)
This known method has a number of disadvantages. The first disadvantage is that a sausage is manufactured in which the organoleptical properties are insufficiently equal to sausage which has been manufactured with a natural or artificial casing which are known in the trade. A second disadvantage is that the method limits itself to the manufacturing of smoked/cooked sausage and fresh sausage. Dried semi-dried and fresh sausage cannot be economically manufactured. A third disadvantage is that usual smoke-and/or cooking installations cannot be used economically in the further processing. With the known method the meat mix is provided with a collagen coverage while with the traditional methods a casing is used which strongly and flexibly encloses the meat mix entirely during the further processing and shapes the sausage.
Further, a similar method is known from the international patent application WO93/12660 whereby it is intended to avoid the aforementioned problems. This method equally includes the steps of coextruding a mainly equal layer of collagen gel around an extruded edible product and the chemical coagulation of the extruded collagen gel while using a chemical coagulation means, though without the step of drying with hot air in order to achieve a coagulated collagen casing around the edible product, which has sufficient strength to allow mechanical separation into individual foodstuff elements which are connected to each other, especially sausages.
Also, with this known method the aforementioned problems and disadvantages have not been resolved adequately. It has been demonstrated that a thus manufactured casing of collagen gel of co-extruded edible foodstuffs, i.e., sausages, has insufficient strength to allow traditional further processing. Furthermore a consequence of low casing strength is that the shape of the sausage rope is not consistent, principally in certain types of further processing. For instance, when strands of edible foodstuffs which are thus manufactured are being hung the partly "fluid" meat mix flows down which gives the edible foodstuffs a cone shape. Such a shape for sausages is undesirable. Additionally, due to the mechanical loading of the gel casing which is not strong enough rupture can occur. Also, the production speed with this known method is disadvantageously influenced by the still insufficient strength and shape rigidity of the casing. An additional disadvantage is that, due to the lengthy stay in the coagulation bath, the salt content in the casing and in the meat mix, is high. This results in unwanted organoleptical and physical changes of the sausage mix, such as in taste, consistency and firmness of the meat mix.
While this known method nevertheless has some attributes in spite of the above disadvantages, it is not capable of replicating the mechanical, physical and organoleptical properties of existing conventional sausages.
The principal purpose of the invention is a method for manufacturing of food strands with an edible casing in which the previous disadvantages of the known methods do not occur.
It is also the purpose of this invention to provide a novel linking method, advantageously used on continuous manufactured edible foodstuff strands, but can also be used in other sausage processing methods.
With the method according to the invention only the outside surface of the gel casing is being dried after the usual steps of co-extrusion and treatment with the coagulation means, by which moisture is being removed from the extruded gel, and the cross-linking of the collagen fibers is being facilitated, and thus the mechanical strength of the gel casing is increased. The strength which is achieved in this way is sufficient to provide a casing which can be further treated in the usual way. In the case of edible foodstuffs, i.e., sausage, manufacturing, it is possible to prepare in this way fresh smoked or cooked edible foodstuffs of which the properties are equal to those of known edible foodstuffs which have been manufactured in a natural or edible or non edible artificial casing.
The moisture content of the casing of the edible foodstuff after leaving the coagulation bath is approximately 90% or higher. With the drying of the outside surface of the gel casing the moisture content is lowered to a value whereby the casing will reach the desired mechanical strength. By adjusting the moisture content the mechanical strength of the casing can be adjusted to the desired value. Maximum strength of the casing can usually be achieved by lowering the moisture content to the range of 40-75%, for example, 50%.
The temperature of the meat under the casing will preferably stay low during the surface drying of certain types of sausages (for example below approximately 35 degrees C.) so that principally no coagulation of the food proteins such as meat proteins will occur. With other types of edible foodstuffs, the coagulation of the meat proteins can be desirable.
The drying of the surface of the formed casing can be effected with appropriate means. A device which is preferably being used for the drying is a surface dryer, whereby the casing is directly being irradiated by a radiation source whereby the moisture which is being removed out of the casing is being conducted away with the help of conditioned airflow. This conditioned airflow also prevents the sausage casing and the underlying meat mixture of being heated to unwanted temperatures. In this way a homogeneous drying of the casing is achieved down to for example 50% moisture in a short time of for example 30 seconds. An appropriate means of radiation is for example a source which emits middle wave infra red radiation.
Advantageously the method is provided with a separation step to separate the strand of foodstuffs into individual elements which are connected with each other. This can be effected in the usual way by crimping, twisting, clipping or tying before or after the surface drying of the strand of foodstuff which is provided with a casing.
In those places, where usually a twist, clip or such like is being used it is advantageous to isolate the individual elements with a chemical clip. In this application a chemical clip consists of a closure made up out of an edible or non-edible non-toxic material. Appropriate materials are for example, polyamide, polyethylene, cellulose and proteins and other natural or artificial polymers. Such a clip can for example occur by titrating, injecting, or spraying an appropriate quantity of an adequate material or materials so that in a short time by hardening a mechanical strong ring is being formed which holds the crimp during the following treatment steps of the strand of foodstuffs.
The invention also concerns a device for the manufacturing of strands of foodstuffs with a casing which is formed out of a protein, especially of sausage strands, which includes means for the co-extrusion of a principally homogeneous coating of gel around an edible product, as well as a coagulation bath for the chemical treatment of the extruded gel coating and transportation means for the transportation of the extruded strand of edible foodstuffs which is characterized in a surface dryer installed after the coagulation bath with a purpose of drying the gel casing.
Existing equipment and processes have other certain shortcomings. Among these shortcomings are extruders which are complex and cannot be easily adjusted so that the diameter of the food strand can be easily adjusted. Helical conveyors used for the strand are open and invite unwanted lateral movement of the strand during movement through the conveyer trough, and contamination is possible. Driers used are not highly efficient and are sometimes detrimental to the quality of the coating material.
It is therefore an object of this invention to provide a continuous food processing system that will permit an elongated strand of meat or the like to be coated with a coating material which is coagulated, crimped, dried, and conveyed in a rapid and efficient manner.
A further object of this invention is to provide an extruder which has a minimum number of parts and which can produce strands of different diameters.
A still further object of this invention is to provide an infrared drier to facilitate coagulation of the coating material.
A still further object of this invention is to provide an efficient crimping means for the coated strand which will not damage the coated edible strand.
A still further object of this invention is to provide a conveying system for an elongated strand of material that is sanitary and free from contamination.
These and other objects will be apparent to those skilled in the art.
The method for the manufacturing of foodstuff strands with a shaped casing of the aforementioned type according to the invention is characterized in fact that after the treatment with a chemical means moisture is being removed from the extruded gel casing through the drying of the exterior surface of the shaped gel casing.